1. Field of the Invention
This invention relates to the manipulation of hierarchical information in a computer system, and more specifically to building an application interface using hierarchical information.
2. Background Art
Software applications designed to run on computer systems allow an application user to manipulate data associated with an application. For example, an accounting application allows a user to manipulate accounting information. A graphical user interface (GUI) is typically designed for a software application that allows an application user to enter and update application data.
Design tools are available that assist an application software developer in designing an application's GUI. However, design tools that are currently available require that the application developer be aware of relationships that exist in the application data.
For example, application data can be managed by a database management system (DBMS) such as a relational database management system (RDBMS). In an RDBMS, data is stored in tables that can be interrelated.
A table can contain multiple rows of data where each row contains one or more fields or columns. Each column contains an item of data. For example, an employee table contains rows of employee records. Each row, or record, contains information regarding an employee. An employee record can contain, for example, a last name column that contains a last name of the employee.
Data stored in a column (or columns) of a table can form the basis for a relationship between that table and another table in the database having a related column (or columns). Using a relationship between columns of two tables, it is possible to join these two tables to provide a single table of information that contains instances of rows from one table combined with related rows from the other table.
Tables may be related via one-to-one, one-to-many, or many-to-one relationships. In a one-to-one relationship, one row in one table is related to a single row in a second table and vice versa. For example, a row in an employee table that contains information about an employee relates to a salaries table that contains the employee's salary information. Since an employee is typically only earning a single salary, there is a one-to-one relationship between an employee's employee table record and the employee's salary table record.
In a one-to-many relationship, a row in one table may be related to many rows in a second table, but each row in the second table matches only one row in the first table. For example, a state table that contains a state identifier and a state name can be related to multiple rows in the employee table. However, a row in the employees table identifies only one state of residence, for example. Conversely, a many-to-one relationship exists where many rows in one table match only one row in a second table, but each row in the second table may match many rows in the first table.
To relate two tables, it is necessary to identify one or more columns that are common to both tables. These columns are typically referred to as keys. A primary key is a unique key within a table and uniquely identifies a row within the table. A foreign key in a second table is comprised of the column(s) containing a first table's primary key information. For example, in the employee table, an employee identifier (employeeID) can be assigned to uniquely identify each employee. The employeeID can be used as a primary key for the employees table. The employeeID can also be used as a foreign key in the salaries table. The employees and salaries tables can be joined by the employeeID columns in each table to have information from both tables available in a single record.
Applications are developed to provide a user with the ability to facilitate access and manipulation of the data contained in a DBMS. A DBMS includes a Data Manipulation Language (DML) such as Structured Query Language (SQL). A DML provides set-oriented relational operations for manipulating data in the DBMS. However, a DML requires a precise syntax that must be used to access and manipulate DBMS data. To use a DML, a user must understand and use the DML's syntax. Instead of requiring each user that wishes to modify data stored in a DBMS to learn the DML's syntax, applications are written that provide an interface between the user and a DBMS' DML. For example, a personnel application provides an interface to allow an employee in the personnel department to view and update employee information.
A database application typically includes a graphical user interface (GUI) that is comprised of presentation elements such as a form. A form is a self-contained presentation element with predefined areas for displaying, entering and/or changing data. The predefined areas are typically referred to as fields.
Fields in a form can be read-only (e.g., a label field). A form can also have fields in which information is displayed and the user can enter information. For example, in an operation to modify an employee's last name, a text field can be used to display the name currently stored in the database and allow the user to overwrite the display to enter the employee's new last name. When user submits the information, the application can retrieve the user input and update the database accordingly.
To populate the fields in a form, the application developer must associate fields in the database with fields in the form. This process is typically referred to as binding database fields with form fields. In a simple example of a form, the fields contained within the form are bound to fields in a single table.
A form can be more complicated where fields receive data from multiple tables. The application developer designing a form must be aware of the relationship(s) that exist between the tables that are to be bound to the fields in the form. If, for example, the form contains fields from tables that are related via a one-to-many relationship, the application developer must design the form the accommodate multiple rows of information. For example, a form that displays a department and its joblistings (which are related via a one-to-many relationship) must be able to display the department information as well as multiple joblistings for that department. The form must be designed to display the department and include multiple rows to display the joblistings for the department, for example.
The relationship between the department and joblistings tables is a one-to-many relationship. That is, there can be many joblistings for a given department. The format of the display of information related by a one-to-many relationship is different than that used to display information related by either a many-to-one or one-to-one relationship.
For example, the employees, salaries and state tables are related to each other via many-to-one (e.g., more than one employee can reside in the same state) and one-to-one relationship (e.g., each employee has a salary). Since a row in the employees table is related to a single row in state and salaries tables, the developer can design a form with fields that display information about an employee taken from these three tables. For example, the form can contain fields to display the employee's name, state of residence and salary.
Thus, it can be seen that the design of a form depends on the type of relationships that exist between the tables. Using existing interface design tools, the application developer has been required to have knowledge of these relationships. The application developer must be aware of the structure of a database including the tables, the columns within a table and the relationships between tables. For example, an application developer that is building a form to display output retrieved from a database must associate fields in the form with columns in the database. If the form includes columns from multiple tables, the developer must be aware of the relationships that exist between the tables which includes the type of relationship.
One example of such a design tool for database applications is the Access product which is available from Microsoft Corporation. Access allows a developer to define the structure of a database and to create forms with fields that are tied to fields in the database. To develop a form, the developer selects a table and fields from the table in the database to include in the form. However, Access does not show relationships between tables. The developer must be aware of the relationships that exist between tables in a database to design an application's interface. This requires that the application developer become knowledgeable as to the structure of the database. This is inefficient. Further, there is the possibility that an application developer will err in generating an interface that cannot accommodate the relationships that exist between the data to be displayed in fields in the interface.